What is the EGG file format?
An .egg file is a proprietary compressed archive created by ALZip and developed by ESTsoft Corp. of South Korea. Introduced as the successor to the older .ALZ format, .egg archives begin with the four-byte ASCII signature EGGA at byte offset 0. The format supports Unicode filenames and multiple compression algorithms - Deflate, Bzip2, LZMA, and ESTsoft's own AZO - and an archive can be split into multiple smaller volumes named .vol1.egg, .vol2.egg, .vol3.egg, and so on.
.egg supports both AES-128 and AES-256 encryption for password-protected archives, and provides a Solid compression option. The Solid mode analyses the file set before determining whether to prioritise compression speed or compression ratio. Per-file CRC checksums allow integrity verification in ALZip and compatible tools.
Although predominantly a Korean-market format, .egg files are frequently encountered when receiving content from Korean senders or websites - the format adopted Unicode and split-volume support earlier than mainstream ZIP. In addition to ALZip, archives can be opened and extracted with Bandizip (Windows, macOS, Android) and PeaZip (Windows).
Security & safety
RISK: MEDIUMEGG is a container, so the risk is whatever it holds - treat unexpected .egg attachments like any archive and scan extracted files before running them (especially .exe inside). Because EGG is niche outside Korea, 'free EGG opener' searches can surface bundled adware/PUP installers; download ALZip only from altools.com and Bandizip only from bandisoft.com. AES-encrypted EGGs need the correct password - there is no legitimate bypass.
Format details
in a nutshell- Python Egg (setuptools) - A ZIP-based Python distribution package (PK signature), unrelated to the ALZip archive; now superseded by .whl wheels.
- Chrome Aura / various game data .egg - A few games and apps use .egg for packed assets; not an ALZip archive.
Programs that open EGG files
Windows3 apps
ALZip
Freemium Native creator - double-click to open and extract. Free for personal use; the original tool for EGG. 
Bandizip
Freemium Right-click the .egg > Extract; or open it to browse. Free version extracts EGG and ALZ fully. Best modern option. 
macOS1 app
Android1 app
Technical details
deep spec| File signature | EGGA (hex 45 47 47 41) at byte offset 0 |
| Byte order | Little-endian |
| Container structure | EGGA header followed by per-file headers and compressed data blocks |
| Compression algorithms | Deflate, Bzip2, LZMA, and ESTsoft proprietary AZO; algorithm selected per file |
| Solid compression | Optional mode; analyses the file set before choosing between compression speed and ratio |
| Encryption | AES-128 and AES-256; legacy ZIP 2.0-style also supported; password-protected archives |
| Filename encoding | Unicode (UTF-16 / UTF-8); supported from the format's inception |
| Split volumes | Volumes named .vol1.egg, .vol2.egg, etc.; no fixed per-volume size ceiling |
| Integrity verification | Per-file CRC checksum; archive integrity test available in ALZip and Bandizip |
| MIME type | application/x-egg (unofficial); application/octet-stream as generic fallback |
| Platform support | Windows (ALZip, Bandizip, PeaZip), macOS (Bandizip), Android (ALZip Mobile, Bandizip) |
| Market origin | Predominantly South Korean; ESTsoft successor to ALZ, common when receiving files from Korean sources |
| Predecessor format | ALZ (.alz), also by ESTsoft - EGG added full Unicode filenames and AES encryption |
| Format version field | EGG header carries an internal version field; ALZip and Bandizip support all versions |
| Released | 2007 (ALZip; succeeding the older ALZ format) |
| Latest version | EGG format used by ALZip 8+ / 10+ |
| Specification | justsolve.archiveteam.org |
EGG conversions
Community Q&A
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